drm/panel-sony-acx424akp: Modernize backlight handling

This converts the internal backlight in the Sony ACX424AKP
driver to do it the canonical way:

- Assign the panel->backlight during probe.
- Let the panel framework handle the backlight.
- Make the backlight .set_brightness() turn the backlight
  off completely if blank.
- Fix some dev_err_probe() use cases along the way.

Tested on the U8500 HREF520 reference design.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210715092808.1100106-1-linus.walleij@linaro.org

drivers/gpu/drm/panel/panel-sony-acx424akp.c

@@ -40,7 +40,6 @@
 struct acx424akp {
 	struct drm_panel panel;
 	struct device *dev;
-	struct backlight_device *bl;
 	struct regulator *supply;
 	struct gpio_desc *reset_gpio;
 	bool video_mode;
@@ -102,6 +101,18 @@ static int acx424akp_set_brightness(struct backlight_device *bl)
 	u8 par;
 	int ret;
 
+	if (backlight_is_blank(bl)) {
+		/* Disable backlight */
+		par = 0x00;
+		ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_WRITE_CONTROL_DISPLAY,
+					 &par, 1);
+		if (ret) {
+			dev_err(acx->dev, "failed to disable display backlight (%d)\n", ret);
+			return ret;
+		}
+		return 0;
+	}
+
 	/* Calculate the PWM duty cycle in n/256's */
 	pwm_ratio = max(((duty_ns * 256) / period_ns) - 1, 1);
 	pwm_div = max(1,
@@ -172,6 +183,12 @@ static const struct backlight_ops acx424akp_bl_ops = {
 	.update_status = acx424akp_set_brightness,
 };
 
+static const struct backlight_properties acx424akp_bl_props = {
+	.type = BACKLIGHT_RAW,
+	.brightness = 512,
+	.max_brightness = 1023,
+};
+
 static int acx424akp_read_id(struct acx424akp *acx)
 {
 	struct mipi_dsi_device *dsi = to_mipi_dsi_device(acx->dev);
@@ -310,8 +327,6 @@ static int acx424akp_prepare(struct drm_panel *panel)
 		}
 	}
 
-	acx->bl->props.power = FB_BLANK_NORMAL;
-
 	return 0;
 
 err_power_off:
@@ -323,18 +338,8 @@ static int acx424akp_unprepare(struct drm_panel *panel)
 {
 	struct acx424akp *acx = panel_to_acx424akp(panel);
 	struct mipi_dsi_device *dsi = to_mipi_dsi_device(acx->dev);
-	u8 par;
 	int ret;
 
-	/* Disable backlight */
-	par = 0x00;
-	ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_WRITE_CONTROL_DISPLAY,
-				 &par, 1);
-	if (ret) {
-		dev_err(acx->dev, "failed to disable display backlight (%d)\n", ret);
-		return ret;
-	}
-
 	ret = mipi_dsi_dcs_set_display_off(dsi);
 	if (ret) {
 		dev_err(acx->dev, "failed to turn display off (%d)\n", ret);
@@ -350,36 +355,10 @@ static int acx424akp_unprepare(struct drm_panel *panel)
 	msleep(85);
 
 	acx424akp_power_off(acx);
-	acx->bl->props.power = FB_BLANK_POWERDOWN;
-
-	return 0;
-}
-
-static int acx424akp_enable(struct drm_panel *panel)
-{
-	struct acx424akp *acx = panel_to_acx424akp(panel);
-
-	/*
-	 * The backlight is on as long as the display is on
-	 * so no use to call backlight_enable() here.
-	 */
-	acx->bl->props.power = FB_BLANK_UNBLANK;
 
 	return 0;
 }
 
-static int acx424akp_disable(struct drm_panel *panel)
-{
-	struct acx424akp *acx = panel_to_acx424akp(panel);
-
-	/*
-	 * The backlight is on as long as the display is on
-	 * so no use to call backlight_disable() here.
-	 */
-	acx->bl->props.power = FB_BLANK_NORMAL;
-
-	return 0;
-}
 
 static int acx424akp_get_modes(struct drm_panel *panel,
 			       struct drm_connector *connector)
@@ -409,10 +388,8 @@ static int acx424akp_get_modes(struct drm_panel *panel,
 }
 
 static const struct drm_panel_funcs acx424akp_drm_funcs = {
-	.disable = acx424akp_disable,
 	.unprepare = acx424akp_unprepare,
 	.prepare = acx424akp_prepare,
-	.enable = acx424akp_enable,
 	.get_modes = acx424akp_get_modes,
 };
 
@@ -458,25 +435,18 @@ static int acx424akp_probe(struct mipi_dsi_device *dsi)
 	/* This asserts RESET by default */
 	acx->reset_gpio = devm_gpiod_get_optional(dev, "reset",
 						  GPIOD_OUT_HIGH);
-	if (IS_ERR(acx->reset_gpio)) {
-		ret = PTR_ERR(acx->reset_gpio);
-		if (ret != -EPROBE_DEFER)
-			dev_err(dev, "failed to request GPIO (%d)\n", ret);
-		return ret;
-	}
+	if (IS_ERR(acx->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(acx->reset_gpio),
+				     "failed to request GPIO\n");
 
 	drm_panel_init(&acx->panel, dev, &acx424akp_drm_funcs,
 		       DRM_MODE_CONNECTOR_DSI);
 
-	acx->bl = devm_backlight_device_register(dev, "acx424akp", dev, acx,
-						 &acx424akp_bl_ops, NULL);
-	if (IS_ERR(acx->bl)) {
-		dev_err(dev, "failed to register backlight device\n");
-		return PTR_ERR(acx->bl);
-	}
-	acx->bl->props.max_brightness = 1023;
-	acx->bl->props.brightness = 512;
-	acx->bl->props.power = FB_BLANK_POWERDOWN;
+	acx->panel.backlight = devm_backlight_device_register(dev, "acx424akp", dev, acx,
+					&acx424akp_bl_ops, &acx424akp_bl_props);
+	if (IS_ERR(acx->panel.backlight))
+		return dev_err_probe(dev, PTR_ERR(acx->panel.backlight),
+				     "failed to register backlight device\n");
 
 	drm_panel_add(&acx->panel);